Coated glazing products having anti-solar properties, that is, low transmittance of to wavelengths in the infra-red range, are known to those skilled in the art. Coatings for glazing products are disclosed, for example, in European patent application 0 646 551 A1 entitled Heat-Treatment Convertible Coated Glass and Method of Converting Same. That document discloses silver coatings comprising a layer Of Si.sub.3 N.sub.4 over a layer of nickel or nichrome, over a layer of silver, over a second layer of nickel or nichrome, over a second layer Of Si.sub.3 N.sub.4. Sputtering is disclosed for producing such coating. Sputtered deposition of a multi-layer coating is described, for example, in European Patent Application 0,418,435 to Nalepka. The multi-layer coating of Hayward et al. is said to comprise a layer of sputtered zinc, tin, titanium, indium/tin or bismuth oxide, next a layer of sputtered silver or silver alloy, then a layer sputtered titanium or stainless steel and finally a layer of zinc, tin, titanium, indium/tin or bismuth oxide. Such multi-layer film is said to have excellent visible light transmission while controlling both near infra-red solar energy and far infra-red reflected energy. A temperable coated article is suggested in U.S. Pat. No. 5,552,180 to Finley et al. The coated article of Finley et al. employs a metal-containing film such as titanium nitride which ordinarily oxidizes at the high temperatures encountered during glass tempering, along with an overcoating of a protective layer of a silicon compound and an undercoating with a stabilizing metal-containing layer. In U.S. Pat. No. 3,990,784 to Gelber a multi-layer coating for architectural glass is suggested, comprising first and second metal layers with a dielectric layer disposed between them. Gelber suggests that the transmission properties of the coating can be changed independent of its reflection properties, by varying the thickness of the metal layers while maintaining the ratio of their thicknesses constant.
Similar coatings are disclosed in European Patent Application 97104710.5 published as EP0796 825 A2, wherein a low emissivity sputtered coating employs controlled index of refraction of an undercoat layer of an appropriate dielectric material below a first Si.sub.3 N.sub.4 layer. Also a layer of silver is used, sandwiched between layers of nichrome. The term "nichrome" is used to designate a layer which includes some combination of nickel and chromium, at least some of which is in its metallic state, although same may be oxidized. In a similar way, the term "silver" means that the layer consists essentially of metallic silver, but may include some other elements in small concentrations that do not adversely affect the performance characteristics of the silver in the system as a whole. Bent or toughened silver coated glass is taught in European Patent Application 87300601.9 published as No. 0233 003. An additional layer of aluminum, titanium, zinc, tantalum or zirconium is used over the silver layer, or both over and under the silver layer. In recent years, the popularity of coated glasses has occasioned numerous attempts to achieve a coated glass article which, prior to heat-treatment, can be coated, and which thereafter, can be heat-treated without adversely changing the characteristics of the coating or the glass itself (i.e., the resulting glass article). One of the reasons for this is, for example, that it can be extremely difficult to achieve a uniform coating on an already bent piece of glass. It is well-known that if a flat glass surface can be coated and thereafter bent, much simpler techniques can be used to get a uniform coating than if the glass has been previously bent. This is true for architectural, automotive, and residential glasses.
Various difficulties have been encountered by those skilled in the art in developing commercially suitable coatings for architectural and automotive glazing. In particular, it has proved difficult to achieve coatings which provide good attenuation of direct solar radiation, that is, good anti-solar properties. There has long been need in the glazing industry for coating systems which can be uniformly deposited, especially by sputtering onto large surface areas with fast deposition rates, low deposition power density, good film quality, including high film durability, bulk or near bulk density, and long shelf life. As used here, large area deposition refers to deposition onto transparent substrates suitable in size for architectural and automotive glazing applications.
It is an object of the present invention to provide coated articles meeting some or all of these industry needs. In particular, it is an object of at least certain preferred embodiments of the invention to provide heat-treatable coated glass articles comprising a substantially transparent glass substrate with a substantially transparent coating on the surface of the substrate, which coating has good transmittance of visible light as well as good anti-solar performance characteristics. In accordance with certain preferred embodiments, it is a further object to provide glazing units incorporating such coated glass. It is an object of at least certain preferred embodiments of the invention to provide heat-treatable coated glass articles comprising a substantially transparent glass substrate with a substantially transparent coating on the surface of the substrate, which coating has medium level of transmittance of visible light as well as extremely high anti-solar performance characteristics. Such coated articles can be used for architectural purposes and automotive applications, e.g., windshields with heat shielding properties, or windshields with defrosting and anti-fogging properties.
It is a further object of the invention to provide methods of manufacturing the aforesaid coated articles. In accordance with preferred embodiments, such manufacturing includes applying a coating in accordance with the invention. Optionally, the methods disclosed here further include the steps of applying an electrically conductive bus bar, if desired, and performing heat treatment of the coated article, e.g., bending or tempering, and also optionally conducting laminating processes.
Additional objects and advantages of the present invention will be readily understood by those skilled in the art given the benefit of the following disclosure of the invention and detailed description of preferred embodiments.